text:
In USAF are people WSO by choice or is it because they didn’t make the cut to be a pilot?
Generally, is a US Air Force Weapon Systems Officer (WSO)

someone who wanted to be an WSO or is specifically assigned and trained to be an WSO from the start, or

someone who failed flight training in some way?

Yoinkman123 I have edited your question to make it a bit more clear. If you disagree with my edit, feel free to roll-back.

Short answer:  #1 is the most correct statement, but it doesn't tell the whole story.  #2 can happen, but it's very rare for the reasons described below.
TL:DR
To understand this you need some understanding of how the USAF personnel system operates. One key factor that constrains how the system operates is that it's designed for a constant flow of personnel through the system where everyone starts at the bottom (for officers, that's a Second Lieutenant). Over time, each year group (people commissioned in the same year) will eventually go before a promotion board. Failure to be promoted normally results in being forced out. Add in people who just quit (after they've met any service commitments), and the year group gets smaller as you move up the ranks. This makes sense as there are fewer people at the top of the chain of command.
The downside to this is that the USAF can't go hire a bunch of 10-year Captains or 15-year Majors if they find themselves short of personnel in that range. So everything in the system is based on long term projections - not just how many do we need today, but 5 or 10 years down the road.
This process is applied to each career field, of which there are dozens. In general, when you start in a career field you will be in that field for your entire career. It is possible to change career fields, but it's not all that common. The biggest factor will be staffing level in your current field and the field you're trying to move into. Moving from an overstaffed field to an understaffed field is possible. The reverse is virtually impossible.
The pilot and WSO careers are complicated by the fact that it has a very long training pipeline and there's an age limit to start the training. So the process of selecting pilot and WSO candidates starts before you ever get commissioned. For the AF Academy and AFROTC cadets, this starts when they enter program where they get to state their desired career field. The number of available slots in each career field are set based on projected needs 5 to 8 years in the future.
Realistically, almost everyone wants to be a pilot. But it can't happen. When I went in the AF limited the pool by setting very high medical standards. The need for uncorrected 20/20 vision cut the candidate pool down to a more manageable size. The standard for WSO/Nav, etc. at that time was 20/70. So WSO was a backup for those who couldn't meet the 20/20 eyesight requirement (or get a waiver). Grades in school as well as performance as a cadet determined whether you got a slot. Some who asked for pilot were offered WSO slots. (I was an engineer and couldn't pass the eyesight for WSO.) And if you screwed up in school, you could lose it the next year.
My senior year (AFROTC) there was a force cut which cut the number of slots. Pilot candidates that lost their slot were given options. Some were offered Nav/WSO or Missile slots, others were given the choice of taking a non-rated career, going in the reserves, or just dropping out of the program with no penalties. I know people that took each of these options.
But even with all this planning, things change. So if you did come in as a non-rated officer, there are some limited opportunities to make it into pilot training. It's a long shot, but if you do really well as a Lieutenant there's usually a few selected each year to become pilots. You don't have much time to do this due to the age limit to start pilot training.
As to the second option, if you were to wash out of pilot training you would not be automatically considered for WSO as that pipeline is likely full. You could apply for it, but again that would be long odds (and the reason for washing out of pilot training would definitely have a bearing on your probability of success.)

If you don’t get promoted you will be decruited?

@Peter That would be one way of stating it. If you don't get selected on your first consideration (in the zone), you'll get another chance with the next promotion group (above the zone). Failing that, you will be forced out. Up through the Major board (10-11 years of service), you'll typically be separated after 6 months. For Lt Col boards and above, you typically get to serve until retirement. Majors can stay until 20 years, Lt Col 28, and Col 30 years. But the rules can be changed based on "the needs of the AF" so some people can be kept on and others pushed out early.

Thanks. Interesting insight. Didn’t expected that it works like this. So you have to get some promotions until you can a lifelong workplace in the USAF.


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Why was the SR-71 made of titanium?
The temperature of the Lockheed SR-71 Blackbird's fuselage never exceeded 500 Celsius, which, to my knowledge, would be perfectly tolerated by stainless steel. So, why titanium?

Titanium is lighter than steel for the same strength, and better able to handle the temperatures than aluminium.

Heavy is bad, light is good. That's the political correctness of aviation.

It's also a very simple-minded to assume that aerodynamic heating dictates structural material. Otherwise why was the space shuttle made of aluminum?

@user3528438 The Space Shuttle's skin temperature could reach 3000°F, hot enough to melt almost all metals. (Tungsten would be fine at that temperature, but is too heavy for an airframe). The Shuttle was protected with a layer of insulation that kept the airframe temperature low enough to use aluminium.

FWIW, most commercial jet bodies are primarily aluminum.

@RobertColumbia While we are on that topic, most commercial jet bodies can be considered tubes of aluminum, and so can most soda cans...

Because the specific strength of titanium at higher temperatures is better than that of steel (both are much better than that of aluminium).

Specific strength vs. temperature is shown on the above graph, from this site. Specific strength is the strength-to-mass ratio, which is the main factor in selecting aeroplane construction material, and it can be seen that:

Titanium alloys have the upper hand until 500 - 600 °C
Aluminium alloys are pretty good as long as the temp does not exceed about 100 °C
For super high temperatures, steel is the only option.

The specific strength issue is of exponential importance for skin panels loaded under compression, as stated in this answer:

With a tension loaded construction, we're only concerned with the cross sectional area: how much force does it see, in order to get to the yield strength. With a compression loaded construction however, the failure mechanism is not yield strength but buckling.
In order to prevent buckling, we need a larger cross section than what would be necessary for pure yield strength, and this cross section is a function of the elasticity modulus, not the yield strength. So now the ratio of weight over elasticity sets the dimension. For compression, aluminium has the best ratio of the three metals mentioned above.

Steel would be the least suitable material for compression loaded panels - corrugating them does increase compression loading limits, but is detrimental for drag.
Plus the last factor: price. Al and Fe alloys cost much less than Ti alloys, and are easier to work with. Therefore, the order of selection of aeroplane construction material is aluminium alloy first, titanium alloy only if really required - which it absolutely was for the SR-71.
---Update---
@MauryMarkowitz mentions in a comment about the problems experienced with two high-speed aeroplanes constructed from stainless steel: The Bristol 188 "Flaming Pencil" and the B-70 Valkyrie.
Image source
The Bristol 188 was intended to fly for extended periods at > M=2, for researching the effects of kinetic heating. The wiki article  mentions how the buckling problem for compression loaded panels was tackled:

The 12% chromium stainless steel with a honeycomb centre was used for the construction of the outer skin, to which no paint was applied. Riveting was a potential method for construction but the new arc welding technique using an argon gas shield known as puddle welding was used. There were long delays with the method, which was less than satisfactory.... North American used the same methods of argon welding of stainless steel honeycomb sheet metal for the XB-70 Valkyrie bomber.

The aeroplane was unfortunately never able to fly at M > 2 for periods long enough to study the kinetic heating effects, and the project was abandoned after some time.
Image source
The XB-70 also experienced problems with the honeycomb structure, again quoted from the wiki:

The first aircraft was found to suffer from weaknesses in the honeycomb panels, primarily due to inexperience with fabrication and quality control of this new material.5 On two occasions, honeycomb panels failed and were torn off during supersonic flight, necessitating a Mach 2.5 limit being placed on the aircraft.[88]
The deficiencies discovered on AV-1 were almost completely solved on the second XB-70, which first flew on 17 July 1965. On 3 January 1966, XB-70 No. 2 attained a speed of Mach 3.05 while flying at 72,000 ft (22,000 m). AV-2 reached a top speed of Mach 3.08 and maintained it for 20 minutes on 12 April 1966.[89] On 19 May 1966, AV-2 reached Mach 3.06 and flew at Mach 3 for 32 minutes, covering 2,400 mi (3,900 km) in 91 minutes of total flight.[90]

The Valkyrie was designed and operational earlier than the SR-71, and it looks like the issues with honeycomb structures plus the development of a more pliable titanium alloy prompted Lockheed to use titanium.

Fun fact: Maximum operational speed of Concorde (Mmo 2.2) was limited by skin temperature of aluminum fuselage. To beat Concorde Tu-144 (Mmo 2.4) had leading edges of titanium alloys even tough it was considerably harder to work with. Soviet Union had also most of the titanium reservoirs. SR-71 program had to buy most of the required titanium from USSR using fake companies.

" Al and Fe alloys cost much less than Ti alloys, and are easier to work with" - well, stainless of that era was having problems of its own. The Bristol 188 proved very difficult to build, and the B-70 had significant problems as well. I'm sure today's methodologies addressed this, but at the time...

CRJ200 uses Ti for the LE Anti-ice piccolo tubes. Paper thin. Rolled and welded. Ti having massive springback, lots of wrap-tension in the tube. Manufacturer decided to change from drilled holes to Electo Discharge Machined holes. EDM holes have a rough burnt radius. Holes started to crack and sections of tube would break apart. Bleed leak was slow to detect and temp control sensors were INBOARD. In some cases the outer 3rd of the wing was not getting heat and airplanes were lying for months with undeiced outer LEs, with just bleed leak snags dispatched as NFF. A miracle nobody crashed.

One minor point - the Bristol 188 is the Flaming Pencil.  The Flying Pencil is the Dornier Do-17.

There is a great article here that breaks it down in depth but its combination of factors made it the best choice, not a single factor (i.e. heat resistance).

But, in reality, the strongest titanium alloys are only about as
strong as the strongest steel alloys. In fact, their temperature
tolerance is actually worse, while Aluminium is lighter. What makes
titanium special is not it’s tensile strength, weight, or
high-temperature performance. It is a combination of all of these
material properties that made it perfect for the SR-71.

Even Lockheed notes here that it was not only the heat but the strength and durability under those conditions that made it the optimal choice.

With anticipated temperatures on the aircraft’s leading edges
exceeding 1,000 degrees Fahrenheit, dealing with the heat raised a
host of seemingly insurmountable design and material challenges.
Titanium alloy was the only option for the airframe —providing the
strength of stainless steel, a relatively light weight, and durability
at the excessive temperatures.
Titanium, however, proved to be a particularly sensitive material from
which to build an airplane. The brittle alloy shattered if mishandled,
which meant great frustration on the Skunk Works assembly line, and
new training classes for Lockheed’s machinists. Conventional
cadmium-plated steel tools, it was soon learned, embrittled the
titanium on contact; so new tools were designed and fabricated—out of
titanium.

Also worth noting, and mentioned here, the expansion characteristics made it ideal for actually construction the aircraft.

All metal expands when heated, it is a part of the chemical property.
Titanium, unlike most metals out there, expands relatively little,
making it the best option for the SR-71 Blackbird. Lockheed knew this
when it designed the plane and specifically designed the aircraft to
fit together better when in flight. When the plane was sitting on the
ground before a flight, it was “cool” and the parts fit loosely into
one another. It wouldn’t be until the plane was in flight and “heated”
up that everything fit snuggly into each other. The large, “cool”
surfaces on the aircraft had a corrugated texture that allowed the
metal to expand as it heated up.

It's worth mentioning, as a general engineering idea, often the material choices are a matter of the best all around optimization of parameters and not a single parameter optimization. There are lots of materials that can withstand high heat, but they are not all practical for building planes.

"the parts fit loosely into one another" - including fuel systems... which is expected to leak fuel on the ground. And fuel in turn had to be special so it can't ignite when it is leaking - all fun exercise for Skunk engineers.

@AlexeiLevenkov you can read about it those exercises in Ben Rich's Skunk Works. He was first an engineer over there under Kelly Johnson, then later ran the place. IIRC, that fuel was way, way better than the liquid hydrogen they tried first.

NASA was the final operator of the Blackbird and this NASA report contains several valuable information about the SR-71. Just download and read it, it has no equation in it and it's written in a really fluent way :) I report here under some parts from the chapter about its structure.
It's worth noting that even if the main requirement driving the choice of the material was obviously the retention of good structural characteristics at high temperature, anyway what tipped the scale was at the end the ability to work with the chosen material: for the North American the scale tipped toward stainless steel when developing the XB-70 Valkyrie; just a couple of years afterwards the scale tipped toward titanium when Lockheed developed the Blackbird; and maybe in the future it will tip toward plastic as Lockheed also explored in the design phase.

Lockheed engineers faced unique challenges in designing and building the Blackbirds. Aerodynamic friction and continuous engine operation during high-speed flight subjected some parts of the airplane to temperatures as high as 1,050 °F. Average surface temperatures ranged from 462 to 622 °F. This precluded the use of aluminum as a basic structural material. The Skunk Works team turned instead to titanium, stainless steel, and other advanced alloys, as well as to high-temperature plastics. Only titanium and steel could withstand the expected operational temperatures, but steel was extremely heavy and Lockheed had little experience with lightweight stainless steel honeycomb structures. Skunk Works technicians realized aged B-120 titanium had nearly twice the strength/density ratio of stainless steel per cubic inch, but weighed approximately half as much. They also found they could manufacture titanium structures with fewer parts using conventional construction methods than were necessary with steel. High-strength composites were not available in 1960. While the Blackbirds featured an abundance of composite plastic laminates as anti-radar treatments, those substances were not used as primary structure.

Fully 93 percent of the Blackbird’s structural weight consisted of titanium alloys.
Three types of titanium alloys were used in the Blackbirds. The first, designated A-A110AT, contains approximately 5 percent aluminum and 2.5 percent tin. The second, B-120VCA, contains approximately 13 percent vanadium, 11 percent chromium, and 3 percent aluminum. Finally, C-120AV contains approximately 6 percent aluminum and 4 percent vanadium. Most of the Blackbirds’ titanium skin, ranging in thickness from 0.020-inch to 0.040-inch, consisted of B-120VCA fastened to the frame by riveting or spot-welding.

Large sections of the leading and trailing edges, vertical stabilizers, chines, and inlet spikes were made of “plastic” laminates of phenyl silane, silicone-asbestos, and fiberglass. These materials – featured primarily on the A-12 and SR-71 families – helped reduce the aircraft’s radar signature.

Areas subject to extremely high temperatures, such as the engine nacelle exhaust ejector section incorporated two types of nickel alloys. René 41 is a nickel base metal alloyed with chromium, iron, molybdenum, cobalt, titanium, and aluminum. It can withstand temperatures up to 1,600 °F. Hastelloy-X – nickel alloyed with chromium, iron, and molybdenum – can withstand approximately 2,200 °F.

Assuming comparable steel alloy from the heat resistance point of view, titanium will be roughly 50% lighter for same structural strength. Considering this, it will become self evident why titanium was chosen over steel or nickel alloys for SR-71, or rather the A-12, the "original" Blackbird.
The Blackbirds were  real gas guzzlers simply because of the drag at high speeds, so a lightweight fuselage was a must to enable large enough fuel capacity for meaningful mission radius.

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If stealth aircraft are invisible to radar, then how do friendlies manage them or see them in flight?
Air traffic controlling is a significant deal when it comes to air forces. If a stealth aircraft like the F-22 Raptor is almost invisible as said, it has cross section of very small metal ball. Then, how do friendlies see their own aircraft in the air? Perhaps GPS/datalink?
As often said, stealth aircraft are not invisible to radar, merely harder to detect. Nonetheless, it will create huge problems for operating an air force to effectively see their own aircrafts in the air.

Perhaps they just turn their transponders on for non-combat operations?

That is my question, are transponders enough?

Not a duplicate, but related: https://aviation.stackexchange.com/q/14373/7532

ADS-b out would be enough.

There are some unofficial stories from the Gulf War relating to this. One of them tells of an F-15 pilot who saw a F-117 whizzing past while his radar screen remained blank.

Like most military aircraft, the F-22 has a military equivalent of a transponder, an IFF system (Wikipedia):

Identification, friend or foe (IFF) is a radar-based identification system designed for command and control. It uses a transponder that listens for an interrogation signal and then sends a response that identifies the broadcaster. It enables military and civilian air traffic control interrogation systems to identify aircraft, vehicles or forces as friendly and to determine their bearing and range from the interrogator.

Depending on mission profile the F-22 may also carry a radar cross section (RCS) enhancer to hide its stealth capabilities and make it more visible on radar.
Usually the main system for creating situational awareness during military operations and training is the Link 16 military tactical datalink. This system is carried by all modern NATO military aircraft, though F-22 will be getting the full feature Link 16 system including transmit functionality during 2021  . Link 16 also utilized by other branches of the military forces.

@manassehkatz-Moving2Codidact IFF still works in an F22

Oh, better start reading the articles I reference with more care. I will update the answer in a bit.

When flying non-combat missions, many low-observability aircraft are fitted with radar reflectors.
Here is a photo of an F-22 Raptor with a Radar Reflector fitted to it. That little Luneburg lens increases the RCS by an order of magnitude!

The role of the Radar Reflector is two-fold. For one thing, it makes the plane visible to other aircraft and to ground stations via radar. Secondly, it denies adversaries the opportunity to test methods of detecting the stealth aircraft.

Can it be removed during flight?

RCS enhancer is not jettisonable.

What's inside the tin?

If the can is empty, how does it fuction as a corner reflector?

I did not claim you said it was a corner reflector, you did however state it is designed to function as one, and I'm interested in how this is achieved. I'm not doubting it is acting like a cr, but I do question the ability of an empty can to efficiently reflect radar waves.

I'm having trouble with your statement "it's empty", when in fact you do not know if it actually is. The device may consist of an outer shell and internal reflective structure, it might even contain electronics. I guess I should formulate a question about this.

Let us continue this discussion in chat.

I've added a link to how the Luneberg lens radar reflector works.

Not Luneberg but Luneburg lens, after the name of the inventor, a professor of optics. It's based on refraction rather than reflection.

Link has rotten. I guess Wikipedia doesn't rot as fast.

@DohnJoe Thank you, rotten link replaced.

A stealth aircraft isn't actually invisible to radar. It's just harder for current radars to see stealthy aircraft at longer distances. This gives a stealthy aircraft the element of surprise against an enemy. So at a long-range a stealthy aircraft radar signature will be a lot smaller than a regular one perhaps the size of a small bird which will get ignored.
However, a small bird flying at Mach one will probably give the game away, lol.
It's always been the case with military attack aircraft in that he who shoots first, usually wins.
Non-stealthy aircraft can employ other techniques to be stealthy or hidden such as low-level flying whereby the ground will obscure you until your close enough as aircraft will be obscured by ground clutter to a scanning radar. Also the curvature of the Earth can obscure you if you fly low enough, you can get as close as 25nm or so before being spotted. Anti-ship missiles employ this technique.
But in open air/space a stealthy aircraft will be picked up a lot later than a non-stealthy one flying toward an enemy monitoring in that direction.
This does not apply to any visual systems as a big hunk of metal in the sky is just as visible. Also, heat-seeking  (infra-red) systems are less affected as heat is heat, and all you can do there is try and mask your heat signature. But these tend to be shorter-range systems.
To answer the question. Friendlies have the exact same problem as the enemy, as they don't have any special radars that can see a stealthy aircraft any better than the enemy can, that is unless you know what you're looking for/listening to.
Security aside the stealthy aircraft will by some means broadcast its location on a random occurrence and securely encoded radio frequency, so as long as you know what to listen for and how to decode it you can work out where your assets are. Obviously, the enemy a) won't know what to listen for and b) know how to decode it.
These details are set on an aircraft pre-flight much like IFF/SSR transponder codes and for obvious reasons are very very secret.
Radars are essentially passive so this limits their range, however, if something is broadcasting the detecting range is increased.
(Simplified example) Think of it as looking for something in the dark (or very low light). Without illumination, you can't see anything until it's up close, but if that thing turns a light on or otherwise illuminates itself then you can see it.
Now if the thing is illuminated all the time everyone can see it which isn't a good idea. So imagine then the light is a certain colour and only you (and the thing) know what colour to expect. Turn the light on for a short time and you can see it as you are looking for it, but its not on long enough for anyone else to figure out there is a light on let alone workout what colour it is. Get the idea :)

This doesn't really seem to answer the question as to how (or if) friendlies track the stealth craft. The degree to which stealth craft are hidden from radar isn't really the focus here. It's more suited as a comment, not an answer.

I updated the question

Stealth reduces the amount of EMR reflected to its source. It's like the opposite of a retro-reflector. Since radar generally works by putting a detector next to an emitter, that makes the aircraft less visible. If EMR is emitted from the aircraft, rather than reflected, as infra-red is, stealth does not affect it. With visible light, not only is stealth not designed to work in that frequency range, but the emitter (the sun) is not next to the detector (your eyes).

@Acccumulation: I'm not sure light is the best example here due to its tendency for diffuse reflection, unless you're specifically assuming a plane made of mirrors.

I was using light as a simple example, its not the best example but most people can relate to it. Either that or its radar theory 101 lol

@Flater My understanding is that stealth works by the plane's surface pretty much acting like a mirror in the radar frequency range. When I said "stealth is not designed to work in that frequency range", that refers specifically to the fact that stealth aircraft do not act as mirrors for visible light.

A stealth plane made of mirrors would indeed be invisible to a detector if the only illumination were next to the detector. Imagine shining a flashlight into a dark room and trying to see a mirror.  If the mirror were specifically designed to not reflect the light back to you, it would be very difficult to detect it.

the radar used by air traffic control systems does actually see the radar reflected from the aircraft in most cases. Instead the aircraft have transponders that transmit a signal when they receive a radar signal. The transponder signal provides additional information useful to air traffic control that would not be available from the reflected radar signal.
If the aircraft is close enough to the radar antenna, they will be the reflected signal. for large aircraft this distance will be larger than for a small aircraft.
The radar cross section is determine how much of the radar signal is reflected. the more stealthy the aircraft the smaller the cross section and the closer it has to be to the antenna to be detected. if a F22 turned off their transponder and did not have a radar enhancer attached, it is doubtful aa air traffic control radar would detect them at all.

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Why would a pilot request that ATC dim the runway lights?
In this clip, the pilot requests dimmed runway lights.

Tower, you able to reduce the runway lights, please?
[Tower dims runway lights]
Thank you much

This seems like a somewhat unusual request.
Why might a pilot request that? Is it because they were literally too bright? Or is there a different reason?

Same reason that you don't want someone driving with their brights on at night, I imagine. :-)

Same reason I dim my dashboard lights when driving at night. (Unless, of course, I'm looking for paradise.)

That is quite a normal request.
Runway lights can be extremely bright because they need to be visible through fog during daylight to provide lateral guidance during take-off and roll-out. See this related answer for some example images.
When the sky is very clear (low humidity / pollution) and it is night, the brightness of these lights at full power will blind the pilots.
Therefore, runway lights are dimmable. But sometimes, even at 5% of power, the lights can still be uncomfortably bright because the pilot's vision is fully adapted to a dark cockpit.

Especially so when flying with a HUD... if the Touchdown Zone lights are overwhelming the HUD symbology, it's nice to have a better choice than to raise the HUD brightness to dazzling high levels.  For a foggy day, that's no concern, and it's good to have the runway lights blasting through the murk, but with a clear & moonless night... absolutely!

@RalphJ Aren’t HUDs projected onto polarized glass? (Maybe even tinted-and-polarized glass?), I’d have thought that alone should ensure good contrast

@Dai  You can control the brightness of the symbology; the brightness of "the world" seen through the combiner isn't reduced (significantly) by the glass itself. That would be undesirable anyway, since sometimes you're scanning for rather dim lights (airport lighting, traffic, weather, whatever) and you don't want the HUD dimming those any further. And, in daylight, you're wearing sunglasses, so you wouldn't want the HUD dimming the view in front of you, more than the view everywhere else.


text:
Why was the skid landing gear located so far aft on the X-15?
The X-15 famously used a pair of steel skids as the main landing gear rather than conventional wheels, which saved weight, allowed the skids to be mounted externally (where wheels and tires would have been destroyed) so they didn't take up internal space, simplified the extension mechanism, etc.

However, they were also mounted very far back compared to most conventional tricycle-gear airplanes. Rather than being just a little ways aft of the CG as usual, they were way back under the tail. This caused some unusual behavior on landing - in addition to giving the pilot almost zero pitch control as soon as the skids touched (since they were directly under the tail, the stabilizer had no lever arm to pivot around them), it did weird things to the landing loads. From NASA book SP-60, "X-15 Research Results":

[T]he extreme-aft location of the main landing skids on the X-15
produces dynamic-response characteristics during landing that are as
unusual as the gear itself.
The primary cause of the unconventional response is the craft's
downward rotation onto the nose gear immediately following the main
gear's touchdown. Significantly, this movement onto the nose gear
causes a subsequent rebound onto the main gear, providing a much
higher load there than that at initial touchdown. In addition, the
nose gear encounters loads that are two to three times greater than at
either of the main-gear skids. Another unique feature is that the gear
loads achieve about the same maximum level whether the pilot
"greases-it-on" or lands with a high rate of descent. These new gear
characteristics have not been without problems. Much study and
analysis of the dynamic response of the airplane during landing has
led to strengthening the gear and back-up structure and modifying the
nose gear so as to provide greater energy absorption.

In other words, there was actually a much higher load through the struts after the nose gear touched down when it settled back than the load from initial skid contact. NASA tech memo X-639 (19630002688 in the NTRS) even comments that if the skids were moved forward it would behave more like a regular fighter jet, but doesn't take that thought any further.
So... why did they choose to put the skids way back there rather than close behind the CG? Was it for better directional stability at touchdown with a sucks-at-low-speeds vertical stabilizer and rudder? Or was it just to provide clearance for the ventral fin stub at high landing AoA while keeping the gear short? Or, was it simply that there wasn't room left for landing gear and the required internal structure at a more conventional location? (Or as it often is, a combination of these or other factors?)

It was used only for landing, so rotation was not a consideration.

Probably nobody anticipated the nose-wheel-bounce-rebound load that would be incurred by the skids.

Googled "Experience with the X15 Adaptive Flight Control System".  The X15 was staticly unstable, as should be expected for an aircraft with a large speed envelope.  It would pitch down as speed increased and pitch up as speed decreased.  The skids were in the back to catch the tail and pivot the aircraft nose down (lowering AoA), and to provide directional stability as it dragged to a stop.  As an (unqualified) observer, carrier tail hooks may do the same thing.

The X-15 landing speed was around 200 mph.  The primary reason to have the skids so far back would be directional stability, which would be helped greatly by a trailing parachute.
The placement of the skids did have an effect of increasing the nosewheel load, resulting in a "see-saw" type of loading back onto the rear skids, but the engineers who marveled at this may have underestimated the contributing loss of wing lift (from lowering of AoA) to the "secondary load peak".
Moving the skids closer to the CG would follow conventional wisdom of "taking it on the mains" but would increase the chance of an uncontrollable nose pitch up if the nose wheel hit first, which would have resulted in a heavy tail strike.  Touching down on the rear skids first would help lower AoA and reduce airspeed before the plane fully touched down$^1$.
A second set of shock absorbing skids near the CG? Possibly.  A landing parachute? Would have helped.  But somehow, on the (sometimes) dry lakebed, they managed.
$^1$ a potential design improvement would allow the elevator to "hold" the two point landing position as speed reduced before the nose touchdown.  This is how tricycle gear normally works.  The Space Shuttle did this slightly better.

Have you been able to find a source stating that the stability was the design intent? The various studies I dug up on the landing gear behavior (written long after design phase, when it was already flying flight tests) seem to hint at the directional stability being the reason, but none state it explicitly.

@CameronSS  in hindsight, one may wonder why the landing apparatus and technique was not more thoroughly evolved, especially since it flew 199 times.  It was the supersonic data they were after, and landing on the lakebed was the way it was done.  Looking into how the X-20 DynaSoar would have been configured.

That's an interesting and useful comparison; per NASA SP-2007-4232, X-20 was planned to have a smooth skid on the nose and wire-brush skids on the mains, specifically for landing stability (to give higher friction on the back, similar to having a nosewheel with smooth skids like X-15). That combined with NASA TN D-1828 "Theoretical Investigation of the Slideout Dynamics of a Vehicle Equipped With a Tricycle Skid-Type Landing-Gear System" definitely seems to imply that directional stability was the driving factor for gear placement.

@CameronSS well, the X-37 (with its computers) seems to have wheeled landings done right.

the X-37 almost leads to the opposite question, I've always thought the main gear looked too far forward to avoid wheelies. I'd love to see a cutaway inside showing how the mass is distributed but obviously that's Very Secret. Maybe it'll get declassified in fifty years and we'll get to have a look...

@RobertDiGiovanni and CameronSS: "directional stability was the driving factor for gear placement". Directional stability would have been given spacing the skids far apart, not locating them far behind the CG. The skids were where they were just to avoid tailstrike and sinking tail at landing. X-37 and space shuttle had wheels on the landing gear, so they cannot be really compared to the X-15 and X-20 but more to conventional airplanes.

@RobertDiGiovanni: since the topic here is landing gear, I'm just talking about the stability during ground roll, not in flight. If you have some comment about my answer please write them under it so that we can talk about it.

@sophit right, that's why they needed drag as far behind CG as possible.  You are correct the X-15 wasn't exactly good at slow flight, and the tail (try this with a paper airplane) progressively drops as it slows down, hence its 200 mph landing speed and "hairy" roll out.  If it went any slower, tail upforce would be insufficient.

@RobertDiGiovanni: hmm, I'm not that convinced... leverarm in respect to CG increases incrementing the distance in respect to the longitudinal axis i.e.spacing the skids far apart; yes, also the position along the longitudinal axis creates a leverarm but I think smaller. P.s.: telling someone to delete their thoughts is really unkind...

@sophit if the landing surface were consistent a wider design might be better, but with a dry lake bed I'd rather have one drag directly behind.  But these were the early days.  Perhaps as a follow on question we can examine the improvements in slow flight and landing subsequent designs made :-).

@RobertDiGiovanni: yes sure, behind the CG as well. Good old days

Indeed as Peter Kämpf said, the skids were only used for landing; the takeoff on X-15 was done by attaching it to the starboard wing of a modified B-52, known as the NB-52A. This was the only way it could takeoff - it couldn't takeoff on its own.

X-15 being deployed from the NB-52A
With that in mind, it makes sense to place the skids as far aft as possible, since doing so maximizes the clearance for the gigantic ventral fin. However, even that was not enough; a large part of the ventral fin had to be jettisoned (it was detachable) before landing in order to have enough clearance. The fin was deployed with a parachute, and with hope that it would land safely so that it could be reused.

If they're already jettisoning a portion of the ventral fin, why not jettison the whole thing? Is that because the larger piece would require a heavier parachute, thus making the whole system heavier?

@dotancohen Probably for structural reasons. Remember, the fins were subjected to extreme speeds and stress. If you made the whole thing removable, there was a chance it could come off in flight, which could doom the aircraft. Losing only part of it would at least afford you some ability to recover.

As already explained in another answer, the main constraint driving the placement of the main landing gear on the X-15 was to avoid tailstrike at landing. But there was also another important effect appearing at landing that precluded locating the main landing gear just behind the CG like in a conventional airplane. A simple overview of the aerodynamic behaviour of the X-15 helps understanding it.

The X-15, like other aircraft of comparable role and era, was designed to collect data at hypersonic speeds, data which was later used in the space shuttle development. And the X-15 was an engineering masterpiece. It was powered by one rocket engine producing 70'000lbf/300 kN of thrust (comparable to an A320), reaching speeds of 4500mph/7000kmh and an altitude of 60mi/100km. It was piloted, among others, by Neil Armstrong. Its nose wasn't pointy like in other supersonic airplanes, but blunt so that the shock wave remained detached from the airplane, lowering its heating. Its skin was made of a nickel alloy which resists extreme pressure and heat but is difficult to machine. It was launched attached under the right wing of a B-52, and when the 45'000ft altitude was reached the X-15 detached from the mothership and ignited its rocket engine. After less than one and a half minutes (!) it was already flying at 160'000ft and Mach 6. It was a marvel designed to smoothly fly at hypersonic speeds.
Anyway, at the low subsonic speeds typical of landing, the X-15 was nothing more that a draggy pipe with some stocky protuberances. After having reached its target speed and height, its rocket engine was exhausted and the X-15 could only glide back toward Earth. The small wing produced lift only in limited quantity, and as a consequence its lift to drag ratio was quite low. It had, therefore, to glide at a quite high angle of attack. So at low subsonic speeds the X-15 was more like a flying squirrel than a hypersonic marvel.
Due to complexity, weight, and precious space occupied inside the fuselage, wheeled landing gears were not an option on such an experimental airplane. Tires' heating would have been an insurmountable problem, too: on the SR-71 for example, the tires of the main landing gear "contained aluminum and were filled with nitrogen. They cost $2,300 and would generally require replacing within 20 missions"; plus the "air-conditioning system was also used to keep the front (nose) landing gear bay cool" (source: Wikipedia). The skin-friction heating increases more or less with the square of the Mach number and since the X-15 was flying at twice the Mach number of the SR-71 it meant a far higher airframe temperature. Main landing gear in the form of simple skids were therefore the only viable solution.
Putting the landing gear just behind the CG like in most conventional design was also not doable: to avoid tailstrike at the high angle of attack of the approaching phase, their struts should have been very long, heavy and bulky (think about the Concorde). So the skids had to be located far back on the fuselage.
But there was also another important aspect to drive the placement of the skids. During approach, in order to compensate for the high AoA and high sink rate, the horizontal stabiliser had to be set at a quite negative deflection to trim the aircraft. Upon touchdown, both the AoA and the sink rate went immediately to zero and the horizontal stabiliser suddenly found itself generating a huge download. Now, if the main landing gear were located just behind the CG like in a conventional design, this huge download on the horizontal tail would have made the aircraft pivot around the main landing gear and sink the tail into the ground. The skids had therefore to be placed well behind the CG to avoid this effect. Theoretically there was an optimal distance behind the CG, somewhere halfway between tail and CG, but it would have been not enough to avoid tailstrike and the skid were finally placed at the far end of the fuselage. This gave the X-15 a quite peculiar landing: upon touchdown with the skids the nose was forced down quite abruptly; then nose suspension got compressed and then extended back pushing the nose up; this up-nose movement downloaded on the skids suspension which then got compressed and extended back as well. After a couple of back and forth jumpings, the X-15 came to slide on the lakebed. This video from Wikipedia shows this behaviour quite well.

Other interesting information about the longitudinal placement of the skids can be found in this NASA report.

Great answer! I'd love to know more about the SR-71 tires, do you have a link to that quote?

@KennSebesta: thanks for your comment and your editing work Yes sure, I forgot to link the source! In this case it's simply Wikipedia.

@KennSebesta: if you are interested, there are many books about the SR-71, I liked the one by Peter Merlin but there are many more

It is worth pointing out that they didn't get a fleet of X-15's, so there were likely extensive constraints on technology, analysis, and and modifications.  If the company only makes 3 as opposed to 300 the economy of scale doesn't support the more in-depth stuff.
When I first saw the question, it looked like the skids were set to protect the tail, and for directional stability.

The skids were indeed set aft to protect the ventral fin; the large ventral fin was a huge problem when it came to landing, and setting the skids aft and jettisoning a part of the fin was what it took to make the landing possible.


text:
What is the "non-apologizing rule"?
I was reading some forum about funny ATC communications and one commentary was

GXXXX: Request status of danger areas X1, 2 and 4
<Pause>
London info: I don't recognise area number x124
GXXXX: My mistake I meant areas x1, x2 and X4
London info (female): Sorry, just had a blonde moment here
(assume she was new and didn't know the non appologising [sic] rule)

(source)
when referring to some thing the ATC said, apologising for not understanding some non-formal phraseology.
What is that rule ?

unnecessary apologies just clutter the frequency

A link to the forum and/or quote of the exact words spoken might improve your chances of getting a good answer. (But I think @ratchetfreak is right.)

yes, edit was right, thanks @ratchet !

I suspect there is no such rule. I looked at a few online sources - none mention the word apology (or variants).
ATC communication is expected to be short and follow a standard set of stock phrase forms.
Anything outside that is discouraged unless necessary to clarify instructions etc.

FAA
An FAA document "Radio Communications Phraseology and Techniques" says

Brevity is important, and contacts should be kept as brief as possible,

So any communication that doesn't follow one of the standard patterns is discouraged. It continues.

but controllers must know what you want to do before they can properly carry out their control duties. And you, the pilot, must know exactly what the controller wants you to do. Since concise phraseology may not always be adequate, use whatever words are necessary to get your message across.

ICAO
An ICAO document "ICAO Standard Phraseology A Quick Reference Guide for Commercial Air Transport Pilots" says

Phraseology has evolved over time and has been carefully developed to provide
  maximum clarity and brevity in communications while ensuring that phrases are
  unambiguous.

Again the emphasis is on brevity and standard phraseology. It also continues ina similar way to the FAA document.

However, while standard phraseology is available to cover most
  routine situations, not every conceivable scenario will be catered for and RTF
  users should be prepared to use plain language when necessary following the
  principle of keeping phrases clear and concise.

Other
For non-pilot rubberneckers like me, a good intro to pilot-ATC communication is a "Say Again" blog post or Two by Don Brown.

I remember one time when I was a young controller and working a slow, high-altitude sector. I was bored so I got into a conversation with a pilot about something or other. All of a sudden I noticed this F-15 was in a big turn.
 "Peach two one, Atlanta Center, where you goin'?"
 "Atlanta Center, Peach two one is declaring an emergency,
        we've lost an engine and are returning to Dobbins."

He couldn't get on the frequency because I was having a conversation.

Wow, that F-15 pilot was having a really bad day. Not only did he lose an engine, but he drew a mission callsign like "Peach." ;)

@dvnrrs yeah i know, and on top of that the atc almost didn't hear him!

@dvnrrs The official state nickname or Georgia is "The Peach State" so it would be unsurprising if, say, the Georgia Air National Guard used "Peach NNN" as a callsign.

@flyingfisch the military guys have the additional problem of being stepped on by us civvies because we can't hear them transmitting on the UHF frequency (but we can hear the ATC responses).

@casey interesting, didn't know they transmitted on different frequencies than civvies

As far as I know, this is not an official rule, but I have heard about it in the past.
I think the 'rule' has its background in two principles:
Firstly, you keep communications efficient and short. Don't block the frequency unnecessary. Some countries have guidance in their ATC communication handbooks that discourage exchange of courtesies. Apologizing could be categorized as such.
For example: in the UK CAA has the following text in their CAP 413 Radiotelephony manual:

Avoid excessive use of courtesies and entering into non-operational
  conversations

Secondly, you don't apologise for asking clarification on the frequency. It implies that you made a mistake. Making sure that the communication is clearly understood by both sides is an essential safety requirement and therefore asking clarification should never be apologised for because it is the only right thing to do when in doubt.
In the context of the eternal pissing contest between pilots and controllers the above is sometimes reduced to following rules:

Never apologize on the frequency
Never call a pilot 'Sir'

It will make THEM feel superior.

In the eternal pissing contest between pilots and controllers the pilots pretty much always win (the worst a controller can do is yell and maybe burden you with some paperwork

Another reason not to call a pilot 'Sir' is you might be wrong. I've been called "Ma'am" on the radio a time or two. I'm a tenor, thank you very much, not an alto.

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text:
What are the advantages of a forward-swept wing over a rearward-swept wing?
What are the advantages of a forward-swept wing vs. a rearward swept one?

Image credit: NASA

Image credit: Paul Maritz / Wikimedia

the forward swept wing will behave more like a triangle wing at supersonic speeds with those smaller wings

in one word: few!

there's a list of forward swept wing airplanes on wikipedia: http://en.wikipedia.org/wiki/Category:Forward-swept-wing_aircraft

The X-29 represented, to some extent, hubris on the part of the control system designers. You can fight nature, but only to some extent.  (This is a good related read from a control system perspective: "Respect the unstable", G. Stein, IEEE Control Systems Magazine, August 2003.)

There have only been a few aircraft built with forward-swept wings. Most notably was the X-29, which you have pictured above. Russia/USSR built one more recently in 1997, the Sukhoi Su-47. One of the biggest claims as to the superiority or an advantage of a forward-swept wing was increased maneuverability. However, in the case of the X-29, as noted in the Flying Qualities Evaluation of the X-29A Research Aircraft,

The high pitch instability of the airframe led to wide predictions of extreme maneuverability. This perception has held up in the years following the end of flight tests. Air Force tests did not support this expectation. For the flight control system to keep the whole system stable, the ability to initiate a maneuver easily needed to be moderated. This was programmed into the flight control system to preserve the ability to stop the pitching rotation and keep the aircraft from departing out of control. As a result, the whole system as flown (with the flight control system in the loop as well) could not be characterized as having any special increased agility. It was concluded that the X-29 could have had increased agility if it had faster control surface actuators and/or larger control surfaces.

The Su-47 was indeed a highly maneuverable aircraft, capable of pulling 9 Gs, however, its immediate predecessor, the Sukhoi Su-37, was capable of pulling 10 Gs. So it's not clear whether a forward swept wing has any real positive impact on maneuverability.
However, stall characteristics are very different. Air tends to travel towards the rearmost end of the wing. On a standard configuration (Rear-swept wing), this of course moves from the wing root to the wingtip. On a forward-swept wing, however, this moves from the wingtip to the wing root.

As a result, the dangerous tip stall condition of a backwards-swept design becomes a safer and more controllable root stall on a forward swept design. This allows full aileron control despite loss of lift, and also means that drag-inducing leading edge slots or other devices are not required. With the air flowing inwards, wingtip vortices and the accompanying drag are reduced, instead the fuselage acts as a very large wing fence and, since wings are generally larger at the root, this improves lift allowing a smaller wing. As a result maneuverability is improved, especially at high angles of attack. At transonic speeds, shockwaves build up first at the root rather than the tip, again helping to ensure effective aileron control.

Because of the capability of the X-29 to have the tips of its wings bend down when at high angles of attack, the X-29 remained controllable at an angle of attack of 67 degrees. However, thanks to modern advances in thrust vectoring, the F-22 Raptor is capable of sustaining an angle of attack over 60 degrees.
With inherent instability and problems with extra stresses on the airplane for only moderate or supposed but not observed gains in instability, it is unlikely we will see combat aircraft with forward swept wings any time in the near future. Other technologies have enabled similar or enhanced performance without the need for novel concepts.

The manoeuvrability you are talking about here is not about being able to pull more G, but about being able to transition from 1 to max G faster. It is caused simply by aft centre of gravity irrespective of wing design (the forward-swept wings just helped to put the centre of lift forward in this case).

Ahhh, thanks for that differentiation. This center of gravity placement causes the pitch instability I mentioned

@JanHudec: The aeroelastic characteristics of forward-swept wings increase any departure from the trimmed state: If it pitches up, the wingtips will twist up and increase the pitch-up moment. But that shifts the control problem now to stopping the pitching motion.

And the x-29 was controlled by a computer.  If it wasn't for the intense computer systems monitoring and adjusting every control surface CONSTANTLY it would crash and burn pretty quickly.

@jedd.ahyoung - not AFAIK. Drones built so far have been primarily for reconnaissance and stand-off attack, areas where maneuverability is not very important at all

Great answer! One small remark. Immediate predesessor of Su-47 is Su-27, from which this design evolved as a future naval aircraft, and not  Su-37, the latest version with thrust vectoring. Back then there was no thrust vectoring, so Su-27 was not as maneurable as Su-47 was expected to be. Nowadays thrust vectoring allows for a greater maneurability and controllability with classic wing design, and this made forward swept wings design inpractical.

Advantages:

The wing spar carry-through can be placed aft of the cabin, so cabin height can be increased. This is important for business-jet sized aircraft.
The boundary layer at the tips is not affected by the inner wing. Controllability can be maintained up to stall.
Aeroelastic effects will increase control commands. This makes for a very responsive airframe.

However, they are directly connected to these disadvantages:

Stall will happen inboard first, which will result in a pitch-up. If the tail cannot compensate, the stall is unrecoverable.
The aeroelastic effects will encourage flutter or divergence. If the speed of that happening is found to be too low, the wing needs to be made stiffer, resulting in a weight increase.

These two disadvantages easily outweigh the advantages for most designs. The first forward swept design, the Junkers 287, needed a massive, wrought wing carry-through for stiffness. Handling was great, but performance overall was poor.

Ju-287 with tufted wings and rockets below the wing engines. The tripod ahead of the vertical holds a faired camera for in-flight observation of the tufts. The unusual engine placement was chosen to optimize lengthwise cross sectional area distribution (long before that was called "area ruling"). (picture source)
If combined with a T-tail, the aft position of the root of a forward swept wing will ensure that the tail is in the wake of the wing root at a high angle of attack, which can result in a deep stall.
The best forward-swept wings can be found in nature: Birds will sweep their wing tips forward if they want to pitch up and create lots of lift. Especially for short landings the forward-swept wing is ideal when the legs are on the ground at the time of wing stall.

An aircraft with swept wings and no washout or washin will pitch up when it stalls no matter whether the wings are swept rearward or forward; for forward-swept aircraft, this is due to the roots stalling first (as you point out), while for rearward-swept aircraft, it's because the wingtips stall first.

@Sean; Yes. Read all about it here.

For a text book overview: http://www.desktop.aero/appliedaero/potential3d/FSW.html
Note that the Hansa Jet actually was a production airliner using the forward swept wing, and 2 glider types that i regulalrly flew also had forward swept wings (for visibility reasons: Schleicher Ka7 and Ka13).
R.

It would be nice if you copied the key points of the linked article into the text.

The forward swept wing in two-seater gliders is mainly to place the rear pilot at the center of gravity, so the plane can be flown by a single pilot without adding ballast. Better visibility is just a pleasant side effect.

The link is dead now.

Also Zlin 142 has forward swept wing.
Not for aerodynamic reasons, but to place the pilots at the center of gravity and the spar behind them.

Blanik L-13 and Scheibe Bergfalke sailplanes had swept-forward wings, it seems it helps in adding freedom in setting center of gravity respect to the pressure center and pilots placement. Advantages of forward swept wings may be mainly in the low speed range, takeoff and landing.
I'm not too sure about Ju-287 being a failure, there are reports it reached 1'000 km/ h in the Soviet hands, good for a bomber, but developing the concept was discontinued, they may have found some heavy problems. A tailless US airplane of the late 40s used this arrangement, NASA/ NACA, Cranfield repository  has documents about it, also YouTube videos exist

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text:
How can I become a pilot in Tanzania?
I am a student in Tanzania and it's required to take PGM (physics, geography and math) to qualify for studying as a pilot. After qualifying, what am I supposed to do to study for a CPL, and what help can I get if my financial status is limited? Are there any scholarships for people in this situation?

people, don't downvote just because the question is not a good fit for the site. have a bit of understanding for a new user who has to learn how the site works in addition to probably having to learn english as a second language.

@Federico In Tanzania, English is often a third language. But I know many Americans with worse English than this person...

I don't really know how civilian or military pilot training takes place in Tanzania, but I might recommend that you make a visit to a fixed base operator at a local airport there in Tanzania and talk with the staff about flight training.  They may be able to assist your further on that path.
A basic Google Search for Flight Training in Tanzania turned up this place.  I don't know how close you are to Dar es Salaam, but they do have a private flight school out there and could better assist you.
As for scholarships for flight training, check these guys out.
Oh, and these guys as well.
Good Luck with your training.

I don't believe the AOPA or the "Fly Accelerated" site has any scholarships outside of the United States. Doing flight training in the United States is not outside the realm of possibility, but it isn't "in Tanzania".


text:
What part of the F-18's wing profile allows for high AoA flight?
I'm trying to analyse the relationship between the angle of attack and lift coefficient of a wing profile I tested. However, I am finding that the data shows that the wing hasn't stalled by the time it reaches an angle of 25 degrees, whereas I am under the impression that a wing usually stalls around 15 degrees. I cannot recall where I have heard it, but I am under the impression that one of the reasons the F-18 is capable of high AoA flight is because of the "surfaces" around the cockpit:

Is that correct? Is high AoA associated with smaller wing width and high chord length?
Also, this is the data I've gathered. I tested the same wing at three different airspeeds. Sorry about the text being in Danish.

Assuming you mean leading edge root extensions (LERX), LEX fences, and  vortices. The answers to this question may be helpful, also this article.

You may also have a look here. It is not the airfoil, but the kind of flow which is provoked by the extended wing roots. The wing is indeed stalled at 25°. And - no excuse needed for adding Danish plots.

You're correct that the leading edge extension (LEX) plays an important part in increasing the maximum angle of attack of the Hornet/Super Hornet. The LEX basically forms a vortex above the main wing, which improves the high angle of attack capabilities by delaying separation. See this question about vortex lift and also another related question.
You can see the LEXs forming vortices over the wing in the following image.

An F/A-18E Super Hornet assigned to Strike Fighter Squadron (VFA) 81 maneuvers over the Nimitz-class aircraft carrier USS Carl Vinson (CVN 70) during an air power demonstration. (U.S. Navy photo by Mass Communication Specialist 2nd Class James R. Evans/Released)

Is high AoA associated with smaller wing width and high chord length?

There is no simple way to answer this question because what matters is not the aspect ratio of the wing per se, but the way the lift is created. In case the wings have high sweepback, the method of lift generation is by vortex lift, which operates in higher angle of attack compared to the normal (moderately swept) wings.
In other cases where the wing sweepback is less, the lift generation will be by conventional means and consequently, the high angle of attack performance will suffer, though this can be remedied by the use of canards, thrust vectoring etc.


text:
What is the weight limit for a pilot to eject from an F-100?
What is the maximum weight for a pilot to use the ejection seat in an F-100 fighter?

I'm amused that it takes FOUR YEARS for a popular aviation website to get it's first user named PILOT. people these days...

@jihyun SE does not require display names to be unique.

@vidarlo I know, just pointing something funny out.

I wonder if there's actual a hard limit. The seat is designed for a specific weight so anywhere away from that increases the risk. But ejection isn't safe anyway so it's not like once out of certain limit then it's guarantee to fail, and there's not a limit to guarantee  a success, either.

How much weight is the seat's rocket motor capable of lifting?  :-P

Firstly, welcome to Aviation Stack Exchange! As for your question, I actually could not find the exact model used for the F-100 series (sorry), but as far as I can tell most American first and second generation jet fighters were installed with Martin-Baker Mk.1-3 ejection seats. These were some of the first examples of explosive charges being used as the main propellant, and for the sake of a shorter answer I will assume you understand their basic operation. The Martin-Baker website states that the for the given size range of crew (between the 5th and 95th percentile), the seat could manage to lift a 224lb pilot/aircrew at a maximum of over 400 knots indicated airspeed.
[Edit] I want to address @GypsyRanger's answer: I think we can all assume that the pilot being ejected from the fighter has undergone and passed Air Force criteria for qualification to be a fighter pilot. I personally think his question is simple but a good one because he is just asking the weight limit, and in terms of mass this shouldn't be too hard to answer. I myself couldn't find the exact model, but all main-stream American jet fighters of the F-100's era were fitted with Martin-Baker seats ranging from the Mk.1 to the Mk.3. If you take the time to look at the specifications for each and compare, or knew beforehand you'd know that the improvements between each model were mostly pertaining to reliability and safety for crew, something that they were lacking in at the time (the firing mechanism was practically the only thing changed throughout). Really though, don't be too quick to criticize if you won't put in the time to read it or because it's a short question.

thanks this is very helpful,  the MB website most useful.  hadnt thought about that.   this is for a ride in a privately owned f-100 backseat for this ol' fighter pilot that has gained a bit of weight...

Ah. As long as you are somewhere close to that recommended range it shouldn't be too much of an issue. Remember, the seat was certified to carry a pilot with a full combat load (all of his gear, survival kit etc) out of a dead fighter at speeds that I'm not sure you'll be even close too. Be safe and have fun though!

Yah, I was 210 when I flew the hun and the sluf and a few others but that was almost 4 decades ago.

Depends on a few variables, including the amount of separating power the ejection seat has, and most of all how tall the pilot is. The current weight limit pertains to and is based on height. Pilots have to meet the Air Force's height, weight and physical conditioning requirements. They must be 64 to 77 inches tall when standing, and 34 to 40 inches tall when sitting. They must weigh 160 to 231 pounds, depending on height. But, the question is a bit too broad because you do not list the variant of the fighter and what type of ejection seat and launching system is used.

Old weight limits were 136 to 213lbs. The F-100 Super Sabre had 4 different variations of the ejection seat.

@RonBeyer oh I was under the impression that only the MB Mk.1 to Mk.3 were used for active role F-100's. What is the fourth?

Do you have a source for the minimum weight and height? A 64 inch tall person would be overweight (almost obese) even with the minimum weight of 160 pounds.


text:
Can I get an FAA restricted ATP certificate with 1000 hours total time?
I have an FAA Commercial Single-Engine certificate with 260 hours total time and a Bachelor's degree in Electrical Engineering issued in Indonesia. I have an Indonesian Passport and I'm working as a copilot flying DHC-6 Twin Otters in Indonesia. I'm planning to get a restricted ATP certificate in the USA but there's a question.
Is it possible to go and get a restricted ATP in the USA after flying 1000 hours TT on DHC 6 Twin Otter in Indonesia?

Are you talking about traning in the US or getting an actual FAA ATPL?

I'm talking about training in the US. I've seen many Nepali Pilots came to the US and getting an FAA ATP training and license with Piper Seneca. The thing is, they have 1500 hours TT before starting the training (that's what they told me). Me, since I have a bachelor degree, I'm thinking about starting the same training like those guys but only with 1000 hours TT. Is it possible?

I changed "ATPL" to "restricted ATP" (or R-ATP, if you prefer), because the FAA doesn't use the term ATPL, as far as I know.

The regulations on restricted ATP (R-ATP) certificates are in 14 CFR 61.160 and it is possible to get one with 1000hrs but only if you attended an FAA-approved school for training. The 1000-hour option is in 61.160(b) and in summary the civilian requirements are:

Hold a Bachelor's degree with an aviation major from an FAA-approved school
Complete 60hrs of FAA-approved coursework
Hold a commercial certificate and instrument rating, both from a Part 141 course

Based on what you've said, it seems unlikely that you meet those requirements so you wouldn't be able to apply for an R-ATP. There's more information from the FAA and this article has a useful overview.
The 'good' news is that your flying time in Indonesia can almost certainly be used to meet the FAA's requirements; they usually don't care where you log time.

Unless you were trained through a military flight school, the answer is no.  Part 61 states that you need a minimum 1500 hors TT to apply for an ATPL unless you either attended a military flight training program or an aviation degree from an accredited institution.


text:
Could an aircraft be tied down, then throttle up and release for takeoff in order to use a shorter runway?
Could airplanes, in theory, be designed to takeoff by first tying the tail to a post, throttling the motors to full power, and then letting loose?
Could it even take off while tied, if the cable is attached to a point that's higher than the tail of the aircraft?

A common short-field technique is to apply the brakes, then go full throttle.  After the engine has reached full speed, release the brakes, and the plane begins moving very quickly for a short takeoff.

Prior to WWII, 2-5 ground handlers would hold the airplane's horizontal stab or wings until full throttle was achieved. This technique not only provided the shortest takeoff, but it also allowed a quick engine test on planes without brakes.

For some time to climb record attempts, the plane was chained down, engines were brought up to full power and then explosive bolts were blown to release it. So the technique is doable, but not of normal use.

As already mentioned, aircraft cannot take off without moving through the air, because it is the airflow around the wing that generates the lift required for take-off, and the only practical way of generating sufficient airflow around the wing is to move the wing through the air. This is typically done by moving the wing, and thus also the fuselage it is attached to, forward.
There is, of course, another way to look at that: aircraft can take off without moving relative to the ground, if exposed to a strong enough wind from the front of the aircraft.
That said, keeping the aircraft stationary, "throttling the motors full power, and then letting lose" is a very common short-field take-off technique at least for propeller aircraft; there's nothing theoretical about that. The aircraft is, however, typically kept stationary by applying full brakes while applying full engine power, rather than by using an external tie-down.
The tail likely isn't designed to take the force of holding the aircraft stationary while the engine is running at full whallop, although there's no reason why such an anchor point couldn't in theory be installed (see motor aircraft towing gliders to altitude, scale up somewhat, and you're close).
Since the brakes are already there and need to be powerful enough to at the very least hold the aircraft stationary during the engine run-up prior to take-off, which happens at a significant fraction of full power and can quite well happen at a hold short point just before the runway, there's no reason to spend weight on reinforcing the tail section to that point. Instead, just use the brakes for the few seconds needed.

Commercial aircraft used to use this technique regularly. As a child*, I remember sitting on the plane listening to the engines spool while not moving, then the sudden sink into the seat as they released the brakes. *This would have been pre-deregulation in the US: early- to mid-1970s.

@FreeMan "Commercial aircraft used to use this technique regularly." Jet or piston?

Jet. Couldn't be explicit on models, but I'd venture to say 707 & 727. As a kid, I distinctly remember the runup, but don't remember other details.

Nope. According to Wikipedia, Ozark Airlines was exclusively DC-9-x by the time I was flying them. (Champaign to LaGuardia via Dulles according to them, but I don't recall ever stopping in Dulles.) According to Wiki, they did order 2 727s but never took delivery.

Jets still do a stationary spoolup in short field conditions AFAIK -- fly out of KSNA sometime if you want to feel this sort of thing.

No, an airplane cannot takeoff while tied to a post.
What creates lift is the speed of the wings through the air.
(or the alternate frame of reference view:  The speed of air over the wings.)
If the plane is tied to a fixed point, like a post, it is not moving in the air, and the wings will not have any lift.

This might be a dumb question, but is it possible for the engines to produce enough wind over the wings for the airplane to take off, despite the plane being on a leash? I'm guessing that that's impossible, but it would be great if you could edit this answer to say so (or to say otherwise).

https://aviation.stackexchange.com/questions/17406/could-a-blown-wing-ever-be-powerful-enough-to-lift-an-aircraft-at-zero-forward-v

https://aviation.stackexchange.com/q/80708/31425

Well that’s part of a catapult launch from a carrier.
The aircraft is held motionless on the cat by a holdback bar attached to the nosewheel or a holdback bridle which is also attached to an anchor point on the flight deck.  The link between the bar or bridle and the aircraft is a frangible metal link, sometimes called the ‘dog bone’ because it is shaped something like a dog biscuit.  It is strong enough to hold the aircraft still, even under full power but fractures when the force of the catapult or EMALS is applied to the airframe during the launch stroke.
For terrestrial takeoffs, I suppose one could do something like that but it is much simpler to just hold the brakes, run up to full power, then release the brakes and perform the takeoff roll.  This is the preferred method of takeoff for light twins and turboprops, as it minimizes the length of the takeoff roll.

Yes.  For example, this F-104C was chained to a truck full of weights, throttled up, and released to set a time-to-altitude record, at Edwards AFB on 1959 Dec 14.  Photo and details from here.

Yes, and not just theoretically. Though not proven practical, specially configured aircraft have been able to hover while restrained, so they obviously could take off in this state. It won't work for just any aircraft but the Ryan/Fairchild VZ3 was designed to do this. In this test, it wasn't tied to a post. Instead a group of people restrained it with a rope.


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What are the pros and cons of practising figure-eight landings on perpendicular runways?
This is just a gee-whiz question, I have no intention of doing this nor am I trying to get anyone's blessing on this.
Part of remaining current to legally take passengers up in a plane is having 3 takeoffs and landings within the prior 90 days. There are also night requirements requiring 3 full-stop landings within the prior 90 days.
Some folks who don't fly often but want to take passengers up will hop in the plane and do 2 touch-and-goes and a full-stop before picking up their passengers. Those same folks might like to be thrifty and do those laps of the pattern as quickly and tightly as possible to minimize tach/hobbs time.
Here's what I'm getting at. If you were based out of an airport with 2 near-perpendicular runways, the winds were calm, and the traffic was nearly if not completely dead, could a pilot do figure-8 shaped landings so that the traffic patterns were halved? This would obviously involve alternating between left- and right-traffic, so those considerations would have to be made as well.
CONS/RISKS:
At an uncontrolled airport, there is some risk of surprising a plane that's not communicating. However, that risk is really not all that different than normal uncontrolled operations.
At a controlled airport, you'd have to get the controller's permission. Unless there's a specific regulation, though, I don't see why they couldn't clear you to land on 09 after taking off from 36.
PROS:
The whole point of these takeoffs and landings is to ensure that you as a pilot are safe to land on runways in general. Taking off and landing 3 times on the same runway does accomplish this, but adding another runway in there makes the currency more "general", especially if there are differing runway surface materials, lengths, widths, etc...
I did assume the winds were calm, but if the winds were something like 5kts, you would also get the experience of having a crosswind. This is great because you might be taking your friends to an airport with one runway, which could mean you have no choice but to deal with a crosswind component. You don't want your first shot at this in 90 days to be with friends in the back!

What precisely are you asking? If it's physically possible? If it has been done? If it's legal?

I'd say the latter two. Maybe someone in here has actually done this and found it to be helpful or an awful idea. Maybe there's a controller in here that knows that this is a definite no-go for some reason.

As a controller I have seen this done and I have offered it to pilots if we were completely dead (as we often are). Some want it in order to practice more actual landings, some don't in order to practice the full pattern circuit. Phraseology after takeoff RY36 would be "Enter left downwind RY09, RY09 cleared for the option."

There's nothing stopping you from doing this at an untowered airfield, at least in the US, UK and most of the places I've flown to. There just isn't any benefit. What you should be looking to do is keep up the practice you need to fly safely, which is the spirit of the law rather than the letter of the law which is to maintain currency within regulation.
Could you fly some weird-ass pattern and save about 5 bucks? Sure! Does cutting corners make you a pilot I'd fly with? Absolutely not, because you are looking for ways to economize rather than fly diligently. Flying the pattern is good because it puts you where other pilots expect you and keeps you out of conflict, it also means you know what to do when you arrive at an airfield for an approach. If you're constantly flying some strange bent figure-eight you're bound to mess it up and that could get you into trouble. Take-offs and landings are the busiest and most dangerous times when flying, the whole point is to standardize and reduce risk, if you are flying to a different runway every time the approach constantly changes which isn't good. A good landing comes from a good approach, which starts from a consistent circuit.
Flying the same pattern is also good for your practice and improving your technique. Flying repeated patterns with the same wind conditions means you practice in those conditions until you nail them. It allows you to hone your technique. If you have a different wind, runway and visual cues every few minutes you don't get the consistency to learn what you're doing wrong and improve it.

All good points! Yeah, I just wanted to bounce the idea off y'all and see if there were some other cons or even some neat benefits to the idea. Just learning!


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Can ATC separate IFR traffic in class A airspace from VFR traffic in class E?
Is it possible for ATC to apply 3 miles separation between an IFR aircraft in class A and a VFR aircraft operating in class E, just below class A?

You mean between Class B and E?  A is only above 18000ft.

Welcome to aviation.SE! Regulations and procedures are different in different countries, so for questions like this please always tell us which country you're asking about.

@JohnK Right, Class A starts at FL180, but just below that is Class E (except at Mt McKinley where it’s Class G right below it). Even KDEN Class B stops at 12000, leaving ~6000ft of Class E

Why would it be any different than any other situation? If they can’t do 3mi. horizontal than they would have to do 1000ft vertical.

Of course it's possible, why couldn't they?

Keep in mind that ATC only separates IFR traffic from other IFR traffic. So they would not provide separation from any VFR traffic no matter what the airspace (with the exception of Class B).
AIM 4−4−11. IFR Separation Standards

b. Separation will be provided between all aircraft operating on IFR
  flight plans except during that part of the flight (outside Class B
  airspace or a TRSA) being conducted on a VFR−on−top/VFR conditions
  clearance. Under these conditions, ATC may issue traffic advisories,
  but it is the sole responsibility of the pilot to be vigilant so as to
  see and avoid other aircraft.

Separation is also provided between IFR and SVFR traffic, but that's a very special (hah!) case.

It is possible but it is not required and not something you should expect to be provided.
Generally speaking (this may vary depending on your country's rules, although I doubt it) VFR operations are permitted in Class E airspace up to but not on the boundary with Class A airspace. In Class E airspace there is no IFR-to-VFR separation requirement, so the controller could choose to provide standard separation between the two aircraft, but would have no responsibility to do so. It is the responsibility of the VFR to remain outside of Class A airspace, and it is the responsibility of the controller to issue traffic advisories if they deem it necessary.


text:
Is a class B endorsement required for a Private checkride?
I was just wondering if a Class B endorsement was required for a Private Pilot Check-ride in the US?

Welcome to aviation.SE! For questions about regulations, please always tell us which country you're asking about.

Sorry, this is in the US.

Do not worry. I have edited the question for you. Please accept or approve the answer. :)

You do not need a Class B endorsement for your PPL Check ride.
By the time you get to you check ride you should have the first 8 endorsements from this list, provided by the FAA.
I will add one caveat to this. During your check ride your examiner will ask you plan a cross country flight. If the route calls for it and you have the endorsement you can plan it through Class B. However if you plan it through Class B your examiner may ask for the endorsement or try and trip you up over it. if you plan a course through Class B without the endorsement the DPE may not stop you when you get in the air. Be careful as you can bust a checkride for this.

Thanks a lot for the information, Dave. Really helps a lot!

Well put, Dave!

There is a later version of 61-65E, dated 1/6/13, vs  the 11/29/05 document  linked to above. Here is the later one: https://www.faa.gov/documentlibrary/media/advisory_circular/ac_61-65e_chg_1.pdf

FAA also has an update Airman Testing Questions & Answers guide, 19 pages of things you might be asking about, so I won't copy it here.  https://www.faa.gov/training_testing/testing/media/questions_answers.pdf


text:
Is a French PAC skydiving license equivalent to an AFF license?
I am planning to do a skydiving course and I was thinking of doing the course in France. That means, I would get a stage PAC license course instead of AFF. I want to know how PAC is different from AFF (previously I have only heard of AFF) and can I use the PAC license to skydive anywhere in the world?

If you mean you are learning to skydive and will be taking PAC instead of AFF, then the differences are minor. IIRC, in PAC the last jump is number 8, whereas in AFF and PFF it's jump 7.
There's also the Canadian version, PFF, and I assume other variations as well. Generally, schools do not follow any of these exactly and add their own variations.

Does it has any difference on where all it is accepted? Is it accepted everywhere in the world if I want to go solo sky diving?

Like any permit, a AFF/PFF/PAC is not international. However, like most licenses, your A-license is. So I would recommend immediately applying for your A-license once you have the 25 jumps. That said, a completed PAC/PFF/AFF along with your logbook is 99% likely going to allow you to jump anywhere in the world, although they may demand a check jump if you have just finished the program.


text:
How can two private pilots flying together log time and split costs legally?
I'm a new private pilot and I've got a neighbor who would like to do some flying in his personal Cessna 172G.  He is a private pilot as well and I am wondering how the regulations apply.
If he sits at the controls as a pilot (not a passenger) and pays for all of the expenses of the flight is that illegal? Even if I am PIC, do the regulations have be considered under pro rata, even he is not a passenger? I'm confused on how the regulations cover this.
He'll also cover the expenses of me flying with a local CFI to get checked out in his 172G, since I built all my time in Citabrias.  I'm confused about the regulations and don't want to do anything that may jeopardize my license.
As far as the arrangement goes, building time would be the closest thing that I could think of. It's his aircraft and he said he would be willing to pay for everything. This could include just local flights, getting a feel for the 172 and building time. I would think he would allow me to borrow it to fly solo as well, once he feels comfortable with me doing that. If it's the two of us just flying around, does it just become a matter of who is PIC? If we discuss that he's PIC and can take over any time, but lets me fly a lot does pro rata still apply? If he's always PIC, then he has to pay at least his share, but could cover all costs. But how does that leave me for logging any time? I'm unsure on how the regulations consider this, since we're both private pilots at the controls.

Welcome to aviation.SE! I don't really understand what you're asking, mainly because it isn't clear what "would like to do some flying" means. Does your neighbor want you to fly him around, e.g. because he doesn't feel comfortable flying himself? Is he offering to fly together so you can both build time while sharing costs? Is he going to let you borrow his aircraft for your own use? The more specific you can be about exactly what the arrangement would be, the more likely you are to get a useful answer.

It would likely be a combination of flying together and letting me borrow it for my own use. I imagine that after I'm checked out with the CFI he knows, that we'll just fly around in the area. When he's comfortable with me in the plane, I'm sure he'd let me get some solo time in it.

Two friends, bumming around in a C172.  Fine and dandy, but only one can log the time.  There is no "commercial" activity apparent here.  Now his insurance coverage is an iffy thing.

Now, when if it comes to me being the one logging the time, does that make him a passenger and we're under pro rata, meaning I have to still pay at least my proportional share? Even if it's his plane, his fuel, oil, and airport expenditures?

@MikeBrass They could both log PIC time as sole manipulator of the controls if they're rated for the C172, e.g. I fly the first 30 minutes, you fly the second 30 minutes, and we both log 0.5 PIC time. Who's acting as PIC is another issue entirely...

Your title question asks about flying together and splitting costs, but then you venture into him paying for everything and you flying solo.  These are two VERY different scenarios.  (sorry, I know this is an old question...)

Short answer: if your neighbor acts as PIC, then he can pay all the costs and you can both log PIC time for however long you were sole manipulator of the controls. But you have to avoid becoming his personal pilot, because then you're getting into commercial territory.

As background, remember that acting as PIC and logging PIC time are different things. And I'm assuming that you're going to fly VFR only, i.e. there are no IFR and/or safety pilot issues (we have a few questions on that already), and that you're both fully qualified to act as PIC (medical, currency etc.).
First, logging PIC time. 14 CFR 61.51 has the rules, and the key one for your scenario is:

(e) Logging pilot-in-command flight time. (1) A sport, recreational,
  private, commercial, or airline transport pilot may log pilot in
  command flight time for flights-
(i) When the pilot is the sole manipulator of the controls of an
  aircraft for which the pilot is rated, or has sport pilot privileges
  for that category and class of aircraft, if the aircraft class rating
  is appropriate;

That means, when you're actually controlling the aircraft then you can log PIC time, regardless of who's acting as PIC. For example, if your neighbor has the controls for 0.5 and then you take them for 0.5, you can each log 0.5 PIC time. But in a single-pilot operation, only one person can log PIC at a time.
Second, sharing costs. Because a C172 is a single-pilot aircraft, if your neighbor is acting as PIC then you're a passenger. Note the wording in 61.113 (emphasis mine):

(a) Except as provided in paragraphs (b) through (h) of this section,
  no person who holds a private pilot certificate may act as pilot in
  command of an aircraft that is carrying passengers or property for
  compensation or hire
[...]
(c) A private pilot may not pay less than the pro rata share of
  the operating expenses of a flight with passengers, provided the
  expenses involve only fuel, oil, airport expenditures, or rental fees.

As you can see, if your neighbor is acting as PIC he must pay at least 50% of those specific costs so he can always pay 100% if he wants; that just comes down to what you agree with him. If you act as PIC then the reverse applies: you must pay at least 50%.
Third, whatever arrangement you have with your neighbor, make sure you don't become a de facto personal pilot. If he starts asking you to fly him places he needs to get to, or even to just accompany him on flights because he isn't comfortable alone, then you should be very cautious. In theory, if he always acts as PIC then it's OK because you're just a passenger. But if there's an accident and the FAA has a reason to believe that he wasn't genuinely acting as PIC then you'll both be in trouble. To take an 'extreme' example, let's say he breaks his leg and asks you to fly him somewhere, with him paying all the costs. He couldn't be acting PIC because of his injury (61.53) therefore you would be acting PIC without paying any costs. That's receiving compensation for carrying a passenger and it requires a commercial certificate.
Finally, a couple of practical points to think about:

Two pilots in a single-pilot aircraft can lead to confusion and even accidents. Make sure you have a good pre-flight briefing that includes who is acting as PIC, and in flight always do a clear exchange of controls. And decide up front what happens in case of an emergency, like engine failure: does the person flying keep flying, or does your neighbor always take the controls?
You should have appropriate insurance. Even if he puts you on his policy as a named pilot you might still have to pay thousands of dollars as a deductible in case of an accident. If you don't already have it, it might be worth getting your own non-owned insurance to cover that, but it all depends on the details of the policies. If you're an AOPA member they can probably help you out with that.

"If you swap controls during the flight then you can both log PIC time for whatever amount of time you were in control." - I found this sentence confusing at first read; I thought you were saying that if you swap controls, then both of you can log PIC time at the same time. Can you edit this answer to clarify that only one person can log PIC time at once (outside of operations that require multiple pilots, and PIC training programs)?

@TannerSwett Thanks for the feedback! I updated my answer, hopefully that point is clearer now.

So when this is really broken down, we can just go fly for the heck of it to get me used to his C172? I guess I envision it as we just go fly with me on the controls most of the time and him staying sharp for any situations that he may need to take control.  Maybe similar to dual instruction but it wouldn't be logged as dual? I figure that as long as we agree he is acting PIC in the preflight and with a positive exchange of controls he will take over in an emergency or a difficult situation that he can pay for 100% of costs.

@ColtonGehman In a word: yes. You can certainly go fly for the heck of it :-) People fly with pilot friends all the time and I don't think your scenario is too unusual.

Just make certain you are operating within the limits of your certificate.  If you are not a CFI, make certain you are not offering instruction, and if you are not part of a Part 135 operation and you don't hold a Commercial certificate, make certain you are not offering to carry passengers for hire from point A to point B - you can share costs but cannot charge any sort of fee.  Are you talking about him assisting you in building your time by allowing you to fly his aircraft, or are you offering a service for hire?  The answer depends on what your intentions are, so remember sentence #1 above.

You might not have meant it this way, but you seem to be implying that a "new private pilot" is allowed to conduct local tours or aerial surveys, which are both usually commercial operations.

Misread his initial question, I saw "Part 141" and assumed he came out with is Commercial, but looked at it again and see he graduated with Private, so yes, this changes my answer a bit.  He can split the bill if sightseeing or letting folks take photos, but with Private cannot do anything for hire so I will clarify that.

@Pondlife reading his question he seems to be looking to offer his friend dual control time, so they both can log the hours. Unless he's a CFI he can't legally do that.

Since he's not a CFI, just PPL, it would just be one of us logging the time I guess.

@jwenting That's not quite correct: assuming they're both rated to fly the C172 then they could both log PIC time for however long they're the sole manipulator of the controls. Instruction is a totally separate issue.

Instruction won't be an issue, he'll set me up to get checked out with a local CFI before we fly together.  However, how does it break down when it comes to cost? Like @Pondlife said, if we each fly 0.5 PIC, how does the cost break down. Is it legal for him to pay for everything or do I still need to deal with my pro rata share?


text:
Is it possible for more than one flight to have the same departure and arrival time slots?
I'm working with real ATFM data such as the planned departure and arrival times of several flights within a given period of time, and I came across a surprising feature.
I found out that some flights have the same departure and arrival time slots. Taking into account that each time slot covers 15 minutes, I was wondering: is it possible for more than one flight to have the same departure and arrival time slots?

Welcome to aviation.SE! I edited your question to clarify the wording, but if I made a mistake then please edit it again, or roll back my changes. And the [tour] may be helpful if you're new to this site.

I assume the answer is yes, otherwise you wouldn't be able to schedule arrivals less than 15 minutes apart. Some airports land aircraft at the rate of 1 or more per minute. This is especially true with airports that have multiple runways that can be used concurrently.

I'm not quite sure what you mean. Besides rather small airports, most airports have quite a bit more than four arrivals/departures per hour (at very large airports, it can be more than 100+ movements/hour at peak). Could you clarify your question?

When I was working at the FedEx hub in Memphis the pushback times were scheduled every six minutes from 1:48 to 4:00. That's 22 slots for well over 100 flights, so there were several scheduled in each slot. They were set up so only one aircraft in any particular section of ramp would be trying to push back at the same time. There would always be a queue at the runway.


text:
How do I calculate the heading to steer in this example?

At 1415 an aircraft was overhead a VOR maintaining radial 215°, en
  route for B, heading 210°(M). At 1430, the pilot decides to return to
  the VOR. The heading to steer is...

The answer is given as 040°(M), I'd just like to know the steps to calculate the answer.

You are holding 215 by compensating for a crosswind using 5 degrees of heading change.
The opposite of 215 is 035.
You must compensate by holding 5 degrees of heading change past 035.

Presumably, the fact that you're 30 minutes flight time away from the VOR when you turn gives the pilot sufficient time to reestablish themelves on course. Thanks @MichaelHall!

The answer is correct if you were to intercept the 215 radial inbound, but the OP should understand that in real life you would have to factor in the space taken up by the radius of turn when reversing course, so proceeding direct to the VOR would yield a different answer.  (the question wasn't specific in this regard...)

@MichaelHall Good point, thank you!


text:
Why are some legs of a SID considered transitions, even when there's only one?
For example, consider the BAYPO8 departure from Tampa (KTPA). The CAMJO waypoint is the final waypoint on a rather linear route that does not contain other final waypoints. The second page of the FAA plate says that CAMJO is a transition.

But if you look at the ENDED8 departure (also from Tampa), there is no such designation on the LACEN waypoint. Although, coincidentally, it was considered a transition in previous AIRAC cycles.

After some digging and exploratory route planning in ForeFlight, it seems I've arrived at an answer that satisfies me: the last waypoint is listed as a transition only if the departure officially ends prior to it, and flying to the transition is optional. If there are other (more correct or plausible) answers, I'd still love to hear them.
The text description of each plate describes where the SID ends. In the case of BAYPO8, the last instruction is on-track to BAYPO. In the case of ENDED8, the text describes on-track to LACEN. So, it would seem that flying to LACEN is required when assigned the ENDED8 departure, however flying to CAMJO is optional for the BAYPO8, because you can drop off the procedure after BAYPO.
This is supported by the route planning features of ForeFlight. When I selected BAYPO8, and then "No Transition," my route of flight for the departure ended at BAYPO. I also had the option to choose the CAMJO transition. This is also supported by analysis of other similar departures that include only one final waypoint option.

The reason for the CAMJO designation as a transition on the BAYPO Eight DP is that there are two possible transitions for the BAYPO DP. A similar comment on the ENDED EIGHT DP isn't needed as there is only one transition fix.
Look at the title of the BAYPO Eight DP.  It is (BAYPO8.BAYPO) which indicates that BAYPO is the transition fix. The CAMJO TRANSITION (BAYPO8.CAMJO) statement on the back indicates that CAMJO is also available as a transition fix. You'll note that BAYPO transition is not listed on the back.
The ENDED EIGHT DP is titled (ENDED8.LACEN). As LACEN is the only transition fix, there is no reason to list it again so it doesn't appear on the back.
Some DPs have several transitions. Typically, the first one is listed in the title with the alternate transitions listed on the back.
If you are loading the departure into an FMS, it loaded sequentially. Select a departure runway and then you can select a DP that works with that runway. Once you select the DP, you can select a transition from the list of transitions for that DP.